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Preparation And Electrochemical Performances Of NiCo2O4/C,TiO2 As Anode Materials For Lithium Ion Batteries

Posted on:2018-07-25Degree:MasterType:Thesis
Country:ChinaCandidate:F F LiFull Text:PDF
GTID:2321330542452652Subject:Polymer Chemistry and Physics
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With the emergence of energy crisis and environmental pollution,the development of clean renewable energy is one of the most decisive technical areas in the future of the world economy.Lithium-ion batteries have the advantages of high working voltage,high energy density,long cycle life,light weight,low self-discharge rate and no pollution.They have been widely used in mobile phones,notebook computers,digital cameras and other fields,like space technology,defense industry.Lithium-ion battery development and improvement of the main direction is to further improve performance and reduce cost,the key lies in the development of high-performance and low-cost electrode materials.In this paper,the latest research background,the challenges encountered in the development process and several mainstream positive and negative electrode materials of Li-ion batteries were summarized first,and the NiCo2O4/C nano-composite material and TiO2 flower ball were prepared by one-step hydrothermal method.The main contents are summarized as follows:NiCo2O4 as a transition metal oxide,the theoretical specific capacity is 900 mAh g-1,the source is rich,cheap and easy to synthesize.NiCo2O4 has the same crystal structure with Co3O4,it is researched because of the better conductivity and lower price compared with Co3O4,but the serious volume expansion during lithium intercalation strongly limits its wide applications in energy storage fields.In this paper,using cobalt chloride as cobalt source and nickel chloride as nickel source,we regulated the amount of the raw material ratio,glucose as well as hydrothermal reaction time,hydrothermal temperature and the calcination conditions such as temperature,atmosphere to prepare a series of different NiCo2O4 and NiCo2O4/C products,which were characterized synthetically by the analyses of phase structure?XRD,XPS?,morphology features?SEM,TEM?and electrochemical lithium-storage performances?charge/discharge,CV,EIS?.The results show that proper amount of glucose?0.5 g?in conjunction with appropriate post-calcination condition can produce NiCo2O4/C nanocomposite material with good rate capability and cycling stability.At a current density of 100mA g-1,the material can charge/discharge the capacities of 634.1/767.2 mAh g-1,corresponding to a coulombic efficiency of 82.7%,and maintain the discharge capacity of 650.1 mAh g-1 after five cycles with a retention rate of 84.74%.Furthermore,at a higher current density of 300 mA g-1,the material can still afford a high reversible capacity of 225.9 mAh g-1.The micro/nano spheres of prepared-TiO2 were synthesized by the method of tetrabutyl titanate?TTIP?as the titanium source and acetic acid as the solvent,and then the prepared-TiO2 was calcined in air at 500?for 3 h to obtain the white powdery material.XRD shows that the material has good crystallinity and is favorable for lithium ion embedding and stripping.From the charge and discharge curve,the first specific discharge capacity is 245.5 mAh g-1,the first specific charge capacity is204.3 mAh g-1,and the first coulomb efficiency is 83.2%,the coulomb efficiencies are all above 97%when the material was cycling 100 turns,which shows high structural stability.In addition,it has excellent magnification performance(the specific capacity of the discharge reaches 86.3 mAh g-1 at a current density of 3350 mA g-1),and this conclusion is verified by testing the cyclic voltammetry curves(0.1 mV s-1-25 mV s-1)at different magnifications,that is,the cyclic voltammetry curves of the composites at different magnifications are very good and have obvious redox peak,which has excellent symmetry,representing the lithium ion embedded and prolapsed reversibly.
Keywords/Search Tags:Lithium ion battery, hydrothermal synthesis, NiCo2O4/C, TiO2, rodlike morphologies, flower ball, in-situ carbon coating, electrochemical performance
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